Description of the Prior Art
U.S. Pat. No. 4,340,592 describes nutrient compositions of dipeptides and tripeptides and the method of administering the compositions to mammals for dietary purposes. The important developments described in U.S. Pat. No. 4,340,592 provide a composition which can be employed to supplement nutritional deficiencies or to provide a complete nutritional composition, particularly for a comatose patient or a patient having metabolic or digestive interference. The introduction of large quantities of free amino acids into a mammal tends to establish hypertonicity and metabolic interference.
The expression "protein nutrients" herein includes free amino acids, organic acid amides of amino acids and oligopeptides.
The nutritional problems arising from using free amino acids could be avoided by employing an aqueous mixture containing oligopeptides, that is, dipeptides or tripeptides, of the essential amino acids and other amino acids wherein the N-terminal amino acid is a glycine residue. The glycine terminal amino acid residue achieves water solubility and achieves excellent absorption of the oligopeptides.
While the use of the described aqueous solution of glycine-terminated dipeptides and tripeptides achieves the objectives set forth, there are some improvements which are useful, particularly in providing a complete nutritional composition
(1) There may be a tendency to develop excess glycine in the patient as a result of using glycine as the N-terminal amino acid residue in all of the oligopeptides. There is no evidence that excess glycine creates any medical problems.
(2) Free amino acids are limitedly soluble in water. Glycine terminated oligopeptides are highly soluble in water. However nutrient compositions containing glycine oligopeptides and/or free amino acids heretofore have been employed in concentrations of 20 weight percent peptide or less, usually less than 15 weight percent total protein content, i.e., the sum of the weight of oligopeptides and the weight of free amino acids. The use of such relatively low concentration aqueous nutrient compositions interferes with development of a complete nutrition system because of the water-intake limits for parenteral nutrition. There is an established limit for the amount of water which can be introduced parenterally into a patient. Approaching that water-intake limit will cause serious problems in medical patients having heart deficiencies or kidney deficiencies. Achieving and exceeding the water-intake limit may be fatal for such patients. Therefore such medical patients cannot be maintained parenterally for extended periods solely by prior art nutrient compositions. Such medical patients heretofore are effectively starving during those periods when they are unable to absorb nutrition except parenterally. It is possible to introduce maintenance-quantities of oligosaccharides, fats, minerals, trace elements and vitamins but it is not possible to introduce sufficient protein ingredients parenterally in the form of free amino acids.